1. Field of the Invention
The present invention relates to an electronic device and interposer board suppressing the propagation of vibration caused by a piezoelectric property and electrostriction and thereby reducing noise, more particularly relates to an electronic device and interposer board suitable for an electronic device including a multilayer ceramic capacitor able to be used for an audio circuit or other circuit sensitive to noise.
2. Description of the Related Art
There have been dazzling advances made in thin film technology and multilayer technology for multilayer ceramic capacitors in recent years. Capacitors having high electrostatic capacities comparable with those of aluminum electrolytic capacitors are being commercialized. As the ceramic materials for forming the multilayer bodies of such multilayer ceramic capacitors, barium titanate and other ferroelectric materials with relatively high dielectric constants are generally being used. These ferroelectric materials, however, have piezoelectric properties and electrostriction properties, so when these ferroelectric materials are subjected to electric fields, stress and mechanical strain occur.
Further, when a multilayer ceramic capacitor using such a ferroelectric material is subjected to an AC voltage, stress and mechanical strain occurring in synchronization with the frequency of the AC voltage appear as vibration. As a result, this vibration is transmitted from the terminal electrodes of the multilayer ceramic capacitor to the board side.
An example of a multilayer ceramic capacitor is shown in FIG. 18. In this multilayer ceramic capacitor 110, two types of internal electrodes are alternately arranged in the multilayer body 112. Terminal electrodes 114, 116 connected to these internal electrodes are arranged at the ends of the multilayer body 112. This capacitor 110 is, for example as shown in FIG. 19 and FIG. 20, mounted on a board 120 so as to connect the terminal electrodes 114, 116 to the interconnect patterns 122 by solder 118.
When such a multilayer ceramic capacitor 110 is subjected to AC voltage, stress P etc. occurs at the multilayer body 112 forming the main part of the multilayer ceramic capacitor 110 and vibration occurs along with this. This vibration is transmitted from the terminal electrodes 114, 116 to the board 120. The board 120 as a whole is liable to become a sound radiating surface and generate vibration sound becoming the noise N.
Such vibration sound has a detrimental effect on the performance and quality of equipment having audio circuits or other circuits sensitive to noise. Therefore, use of multilayer ceramic capacitors using ferroelectric materials for such equipment has generally been avoided.
Note that the technologies disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2000-235931, Japanese Unexamined Patent Publication (Kokai) No. 9-246083, Japanese Unexamined Patent Publication (Kokai) No. 6-55752, Japanese unexamined Patent Publication (Kokai) No. 2000-232030, Japanese Unexamined Patent Publication (Kokai) No. 2000-223357, and Japanese Unexamined Patent Publication (Kokai) No. 2000-182887 are known. However, the inventions disclosed in these publications are insufficient in respect to the suppression of the propagation of vibration caused due to the piezoelectric property and electrostriction and the reduction of noise.
An object of the present invention is to provide an electronic device able to suppress the propagation of vibration occurring due to a piezoelectric property and electrostriction and thereby reduce the occurrence of noise and an interposer board used for such an electronic device.
To achieve the above object, according to a first aspect of the present invention, there is provided an electronic device having a body having a pair of terminal electrodes and an interposer board to a front surface of which the pair of terminal electrodes are connected and having on its back surface a pair of external electrodes electrically connected to the parts where the pair of terminal electrodes are connected, wherein the terminal electrodes and the external electrodes are arranged in a positional relationship where the direction of a line connecting the pair of terminal electrodes and the direction of a line connecting the pair of external electrodes intersect.
Preferably, a pair of land patterns to which the pair of terminal electrodes are to be connected are provided on the front surface of the interposer board, and these land patterns and external electrodes are arranged in a positional relationship where the direction of a line connecting the pair of land patterns and the direction of the line connecting the pair of external electrodes intersect.
According to a second aspect of the present invention, there is provided an interposer board to a front surface of which a pair of terminal electrodes are to be connected and having on its back surface a pair of external electrodes electrically connected to parts where the pair of terminal electrodes are connected, wherein a pair of land patterns to which the pair of terminal electrodes are to be connected are provided on a front surface of said interposer board, and these land patterns and external electrodes are arranged in a positional relationship where the direction of a line connecting the pair of land patterns and the direction of the line connecting the pair of external electrodes intersect.
In the interposer board and electronic device according to the present invention, the back surface of the interposer board is provided with a pair of external electrodes connected to the parts where the pair of terminal electrodes are connected, and these are arranged in a positional relationship where the direction of a line connecting the pair of land patterns and the direction of the line connecting the pair of external electrodes intersect. Further, the electronic device is mounted on an external board by the pair of external electrodes being connected to the interconnect patterns of the external board.
Along with application of an AC voltage to an electronic device, vibration occurs due to the piezoelectric property and electrostriction of the body. In the present invention, however, since the direction of the line connecting the pair of terminal electrodes of the body and the direction of the line connecting the pair of external electrodes of the interposer board intersect, the propagation of the vibration to the external board becoming the sound radiating surface is suppressed and generation of noise from the substrate is reduced.
That is, in the present invention, by just adding the interposer board to the body and connecting the body to the external board through the interposer board, vibration transmitted from the pair of external terminals of the interposer board to the external board can be reduced and the generation of noise from the external board can be reduced. This is because the direction of vibration of the body mainly matches with the direction of the line connecting the terminal electrodes and the direction of vibration does not match with the direction of the line connecting the pair of external terminals of the interposer board.
Preferably, the pair of terminal electrodes in the body and the interposer board are connected by high temperature solder or a conductive adhesive. By the pair of terminal electrodes and the interposer board being connected by the high temperature solder or conductive adhesive, these are mechanically connected while securing conductivity.
Preferably, the front and back surfaces of the interposer board are provided with conductor patterns, solder resist is coated on the surfaces of the conductor patterns to expose at least part of the surfaces of the conductor patterns, and as a result the pair of land patterns are formed on the front surface of the interposer board and the pair of external electrodes are formed on the back surface of the interposer board. Preferably, connecting electrodes connecting the conductor patterns present on the front and back surfaces of the interposer board are provided on the interposer board. By this configuration, the pair of land patterns and the pair of external electrodes are reliably electrically connected.
Preferably, the connecting electrodes are through hole electrodes passing through the interposer board. The rigidity of the interposer board drops due to the presence of through hole electrodes, so this interposer board can further reduce vibration.
Preferably, the ends of the interposer board are recessed and the connecting electrodes are arranged in the recessed parts. By arranging the connecting electrodes in the recessed parts of the interposer board, the connecting electrodes can also serve as external electrodes. Along with this, there is no longer a need for using through hole electrodes.
Preferably, the electronic device of the present invention has a plurality of such bodies and the plurality of such bodies are arranged on such an interposer board. The plurality of bodies may also be arranged stacked. By arranging a plurality of bodies, an electronic device having a higher electrostatic capacity can be easily obtained and replacement of aluminum electrolytic capacitors becomes even easier.
The body is not particularly limited, but for example multi layer ceramic capacitor, chip-type tantalum electrolytic capacitor, chip-type film capacitor, chip-type aluminum electrolytic capacitor, etc. may be mentioned. Preferably, it is a multilayer ceramic capacitor.